Valuable Chinese Market Becomes
Tougher Nut to Crack for Ad Firms

C HINA IS one of the fastest-growing advertising markets in the world, but it is slowing down, making it even tougher for multinational advertising agencies to earn profits there.

Last year, China surpassed Korea to become Asia's second-biggest ad market, after Japan. Advertisers spent more than $5 billion there, according to the AC Nielsen market research firm. Ten years ago, the world's most populous country wasn't even in the top...